This invention is generally directed to a system for controlling and detecting an agglutination reaction and, in particular, to providing a system that creates a controlled isoplanar agglutination reaction that is optoelectronically detected.
Agglutination reagents have been used in recent years for diagnostic test purposes in the immunochemical field. Immunochemical testing is used for detecting certain molecules, the presence of which are indicative of such conditions as human pregnancy, various infectous diseases, allergenic conditions, etc. In testing for the conditions aforenoted, it is desired that objectivity and reproducibility be maximized and subjectivity and nonreproducibility be minimized.
Heretofore neither optimum sensitivity nor reproducibility have been obtainable, by reason of the manner in which such immunoassay reactions have been performed and evaluated. For example, the most common method of testing for conditions using an agglutination reagent is to manually react the reagents on a slide or in a test tube and to evaluate the agglutination reaction (i.e., agglutination or non-agglutination,) with the unaided eye. Such methods of manual testing rely entirely upon the visual acuity of the person doing the testing. Not only is sensitivity and reproducibility not attainable from individual-to-individual, but even the same individual conducting a series of tests cannot eliminate one's inherent subjectivity.
In order to overcome the subjectivity inherent in manually analysing an agglutination test, efforts have been made to lessen the subjectivity of manual testing by the utilization of known instrumentation in the diagnostic field. One such test method uses a spectrophotometer to measure the agglutination reaction in a spectrophotometer cell (a test tube). It is noted however that a standard spectrophotometer cell has a thickness on the order of 1 centimeter (10,000.mu.). It has been found that known agglutination reagents, when placed in a spectrophotometer cell having a thickness on the order of 1 centimeter, have an optical absorbance that is in excess of the limits of conventional machine readability and, hence, cannot be read by conventional spectrophotometers.
Accordingly, it is necessary to dilute known existing reagents by 10.sup.2 in order to permit the reagents to be within the range of a spectrophotometer. However, dilution on a magnitude of the type necessary to be readable by a spectrophotometer not only can seriously hamper the sensitivity obtainable by the reaction but also precludes monitoring of a rate reaction on a continuous basis by reason of the intervention necessary to dilute the reagent to obtain a reading by the spectrophotometer. Moreover, an additional disadvantage of using a spectrophotometer is that it only reads the agglutination reaction, if any, that occurs and does not in any way reliably control the reaction conditions and assure repeated reproducibility of the result. Still a further disadvantage of diluting known existing reagents by 10.sup.2 in order to permit the reagents to be within range of a spectrophotometer is that the speed of the reaction will be greatly reduced many orders of magnitudes to the speed of reaction obtainable when the reagents are not diluted. Accordingly, an agglutination reagent detection system that is capable of controlling the rate of agglutination and is further capable of detecting an agglutination reaction without dilution of the agglutination reagent is desired.